<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="box">123</div>
    <script>
        // 'use strict'
      let abc = 100
      console.log(abc)

      function test() {
        console.log('this:', this)//没有调用者在严格模式上为undefined，非严格模式为window
      }

      test()

      let obj = { name: '文理东', age: 88 }
      delete abc  
      delete obj.age //可以删属性和方法，不能删变量
      console.log(obj)
      console.log(abc)
    </script>
</body>
</html>